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Integrated circuit with diode-connected transistor for reducing ESD damage

  • US 5,446,302 A
  • Filed: 12/14/1993
  • Issued: 08/29/1995
  • Est. Priority Date: 12/14/1993
  • Status: Expired due to Term
First Claim
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1. An integrated-circuit (IC) chip comprising circuitry including elements such as transistors, capacitors or resistors, said circuitry being connected by a lead to an external terminal point of said IC chip, said IC chip further being formed with a clamp device to reduce damage to at least one of said elements of said circuitry from electrostatic discharge (ESD) striking said terminal point, said clamp device being formed during the formation of said circuit elements of the chip and including;

  • a cell defining a semiconductive region for said clamp device and having a circular cross-section so as to form a right-circular cylindrical configuration having upper and lower regions at opposite ends of the axis of said cylindrical configuration;

    said upper and lower regions having top and bottom surfaces respectively at the ends of said axis, and having side surfaces extending around the circumference of said cell;

    dielectric isolation means surrounding said cell at said top, bottom and side surfaces thereof;

    a vertical bipolar transistor formed in said cell and comprising;

    a well with dopant of one type in said upper region of said cell and having an upper surface in contact with said top dielectric isolation means;

    said well serving at least as a part of a collector for said vertical bipolar transistor;

    a region of semiconductive material of circular cross-section having dopant of type opposite said one type and formed in said well adjacent said top surface to serve as the base of said bipolar transistor, said base being concentric with the right-circular cylindrical configuration of said cell, and further having an upper surface in contact with the dielectric isolation means at said top surface;

    base contact means in the center of said circular base region, said base contact means being highly doped with dopant of said opposite type to establish a contact for making electrical connection to said base;

    an annular emitter concentrically arranged in said circular base region around said base contact means;

    said emitter being spaced radially from said base contact means such that at least part of said base region is between said base contact means and said emitter;

    means conductively connecting said base contact means and said emitter;

    means to establish a contact for said region functioning as a collector;

    means connecting one of said contacts to a low-impedance bus; and

    means connecting the other of said contacts to said lead between said terminal point and said IC circuitry so as to shunt electrostatic energy received from said terminal point thereby to prevent damage to said IC circuitry.

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